Except in the case of a fraudulent return or of neglect or refusal to make a return, every deficiency must be assessed within 3 years from the due date of the return or the date of filing the return, whichever period expires later.
Mont. Code Ann. § 15-70-421, under Gasoline and Special Fuel Tax.
Mont. Code Ann. § 15-70-421
Except in the case of a fraudulent return or of neglect or refusal to make a return, every deficiency must be assessed within 3 years from the due date of the return or the date of filing the return, whichever period expires later.